1. Field of the Invention
The present invention relates generally to decoding in a wireless communication system, and more particularly, to a method and apparatus for controlling decoding in a Modulator-Demodulator (MODEM) chip.
2. Description of the Related Art
The most prevalent technologies for providing data service to users in today's wireless communication environment are 2.5th Generation (2.5G) or 3rd Generation (3G) cellular mobile communication technologies and Wireless Local Area Network (WLAN) technologies. The 2.5G or 3G cellular mobile communication technologies include Code Division Multiple Access 2000 1xEvolution Data Only (CDMA2000 1xEVDO), General Packet Radio Services (GPRS), and Universal Mobile Telecommunication Service (UMTS), and the WLAN technologies include Institute of Electrical and Electronics Engineers (IEEE) 802.11 WLAN.
The most prominent feature of the 3.5G cellular mobile communication technologies is that packet data service is provided to users so that they can access the Internet in a wide wireless communication environment. These wireless communication systems provide High Rate Packet Data (HRPD). A system supporting HRPD (an HRPD system) sends one coded packet over a plurality of slots. The number of slots that one packet occupies is defined as a slot size or a span.
In a wireless communication system, for example, the HRPD system, when a receiver has received data in as many slots as a span set in system, it ends decoding for error correction of received data. This is called “Normal Termination”. The Normal Termination is made irrespective of the decoding result of the received data. On the other hand, the receiver can end decoding according to the decoding result even before completely receiving data in as many slots as the span. For example, when the decoding result is “good”, the receiver ends the decoding without further receiving the data of the remaining slots. This is called “Early Termination”.
FIG. 1 is a flowchart illustrating a decoding procedure in a typical wireless communication system. By way of example, a Mobile Equipment (ME) receives data from a Base Station (BS) and performs the decoding procedure in the illustrated case of FIG. 1.
Referring to FIG. 1, the ME receives data in a slot associated with a packet in step 101 and recovers the packet by decoding the received data in step 103. If the ME received data in at least one previous slot associated with the packet, it combines the data of all the previous slots received in relation to the packet before the decoding. In step 105, the ME compares the number of slots received so far (received slots) with the span of the packet. If the span is less than the number of the received slots, the ME normally terminates the decoding of the packet in step 107.
On the contrary, if the span is equal to or greater than the number of the received slots, the ME determines whether the decoding result is “good” or “bad” in step 111. If the decoding result is bad, the ME returns to step 101 to receive data in the next slot associated with the packet. If the decoding result is good, the ME early terminates the decoding of the packet in step 113.
In the HRPD system, as described above, for the case of early termination of decoding, a decoder, for example a turbo decoder of the ME such as an Access Terminal (AT), decodes received data in every slot and determines whether the decoding result is good or bad.
Given a packet format specifying a span of 16 slots, the turbo decoder decodes even when data is received in the first slot. Also, even when all of the 16 slots should be received, i.e. in the case of normal termination, the turbo decoder decodes data in every slot.
In the case of early termination of decoding, the turbo decoder decodes received data in every slot irrespective of the packet format of the data. This unnecessary decoding consumes the power of a MODEM chip. For its operation, the turbo decoder occupies a relatively high 10% of the total power consumption of the MODEM chip and the conventional HRPD system dissipates about 9.4% of the total power consumption of the MODEM chip for the unnecessary decoding.